BEIRUT, JUNE 19 -- --

Syrian security officials stepped up secret contacts and indirect pressure for the release of American newsman Charles Glass, who was seized by gunmen along with the son of Lebanon's defense minister and their driver Wednesday, a source close to the Syrians said today.

Two persons were killed tonight during an outburst of fighting in the Shiite Moslem-dominated southern suburbs of Beirut between the moderate Shiite Amal militia -- Syria's main ally in Lebanon -- and a clan affiliated with the radical, pro-Iranian Hezbollah (Party of God).

Amal security commanders were reluctant to link the sudden, though limited, fighting to Syrian efforts to win freedom for Glass. Syria deployed 7,500 troops in Moslem-controlled west Beirut last February but has thus far been unwilling to enter the southern suburbs, a Hezbollah stronghold and the area in which most of the nine U.S. citizens kidnaped in Lebanon are believed to be held.

Glass, 36, Ali Osseiran, 40, the son of Lebanese Defense Minister Adel Osseiran, and his driver, Ali Suleiman, were kidnaped along a coastal road at Ouzai, on the edge of the southern suburbs.

A source close to Syrian military intelligence and observers in Lebanon said tonight that the kidnapers were trying to strike a bargain -- maneuvering to discharge Osseiran but keep Glass as a hostage -- an offer that has been rejected by the Osseiran family and the Syrians.

The source said that Syrian military authorities in charge of the Glass case would settle for nothing less than freedom for the American journalist, who became the first foreigner to be abducted since Syrian troops were deployed here.

The source said a clear warning had been issued to the kidnapers "via contacts made by the Syrian command through certain channels."

An implicit threat communicated to the kidnapers notes that "the abduction of the American journalist Charles Glass is directed against those supervising a security plan here, namely the Syrians," he added. The kidnapers were "advised to end the affair in an appropriate manner," the source said.

Defense Minister Osseiran said he had been advised that the three captives were being held by the Tehran-linked Hezbollah. "I insist that they all be released," Osseiran said today.

A pro-Syrian militia leader accused the group outright and told journalists the three victims had been moved from one hiding place to another in Hayy Madi, a slum neighborhood in the heart of the southern suburbs.

"Hezbollah is behind the kidnaping . . . This action has put them in the spotlight," said Assem Kansou, head of the Lebanese wing of the Syrian Baath Arab Socialist Party.

The kidnaping of Glass has highlighted an ongoing tug-of-war between prestige-conscious Syria and local Shiite groups such as Hezbollah that maintain close links with Iran. Tensions have remained high between Damascus and Hezbollah since Feb. 23, when more than 20 Hezbollah supporters were killed in a clash with Syrian forces here.

Wednesday's kidnaping dealt a blow to Syrian prestige, especially since Syrian Army commanders had declared that west Beirut was safe for westerners.

"We came to Lebanon because the Syrians invited us," said Mary Curtius, an American correspondent for the Christian Science Monitor who dined with Glass on the eve of his abduction.

Robin Lustig, the Middle East correspondent for the London Observer, said he had traveled to Beirut because he was encouraged by the fact that the "Syrian Army seemed to be in control" and the militias had apparently vanished from the streets.